Axolotl Morph Guide

The Albino locus controls melanin synthesis via the tyrosinase enzyme. Homozygous recessive (a/a) animals completely lack the ability to synthesize melanin, eliminating all melanophore pigmentation. Xanthophores and iridophores remain functional, so an otherwise wild-type albino (D/- a/a) appears golden yellow with iridescent speckling and pink/red eyes. The "Golden Albino" phenotype. When combined with leucistic (d/d a/a), the result is the "White Albino". A white animal with pink/red eyes and no dark pigment or freckling.

The Axanthic locus controls xanthophore function. Homozygous recessive (ax/ax) animals have xanthophores that are unable to produce pteridines (yellow pigment), though the xanthophores themselves are still present and can store small amounts of dietary yellow pigments. The result is a gray to silver animal with dark melanophores and iridophores but little to no yellow coloration. Axanthic axolotls can appear similar to dark wild types, especially melanoid axanthics, making genotype confirmation from parents important.

The Copper locus controls eumelanin maturation via the Tyrp1 enzyme. Homozygous recessive (cu/cu) animals cannot fully oxidize eumelanin, producing pheomelanin (brown/red pigment) instead of eumelanin (black pigment). The result is a warm brown to copper-colored body with lighter eyes, functional xanthophores (yellow), and iridophores (iridescent). Copper axolotls are sometimes described as a form of tyrosinase-positive albinism because melanin synthesis initiates but cannot complete the full pathway to eumelanin.

The Dark locus controls melanophore migration and differentiation during embryonic development. Wild type (D/-) allows normal melanophore distribution across the body. Homozygous recessive (d/d) results in the leucistic phenotype: melanophores fail to migrate from the neural crest into the skin, producing a white or pale pink animal with dark eyes. Leucistic axolotls retain the ability to synthesize melanin (unlike albinos) and commonly develop scattered dark freckles or patches on the head, gills, and dorsal crest as they mature. The d/d phenotype is the most popular and recognizable axolotl color morph in the pet trade.

Green Fluorescent Protein transgene. GFP-positive axolotls express a fluorescent protein originally derived from the jellyfish Aequorea victoria. Under normal visible light, GFP axolotls appear identical to their non-GFP counterparts. Under blue or ultraviolet light, GFP-expressing tissues fluoresce bright green. The transgene segregates as a dominant trait: one copy (hemizygous/heterozygous) produces visible fluorescence. GFP can be combined with any base color morph. The fluorescence is visible in all chromatophore backgrounds, though it is most dramatic in lighter morphs (leucistic, albino) where the green glow contrasts against the pale body.

The Melanoid locus controls iridophore differentiation. Homozygous recessive (m/m) animals lack iridophores entirely, which eliminates the shiny/iridescent speckling seen in wild type axolotls. The absence of iridophores also triggers a secondary effect: some xanthophores convert to melanophores, resulting in increased eumelanin deposition and reduced yellow pigment. The net effect is a uniformly dark gray to jet black animal with no iridescent highlights and minimal yellow. Melanoid is one of the most visually striking axolotl morphs.